In recent years, the use of mobile phones, “smartphones”, laptops and tablets for wireless communication of speech and data has grown immensely such that the demands for capacity, performance and flexibility in public cellular networks for radio communication has increased dramatically to meet this growth. The capacity of a cellular network is dependent on a range of factors such as the number and size of cells, available radio bandwidth, usage of radio resources, configuration of hardware and software, and so forth. For example, multiple small cells may be introduced in addition to a large macro cell to increase capacity locally in limited areas with dense traffic, hence referred to as “hot spots”, within the macro cell. Such small cells within a macro cell are often referred to as “pico cells” although other similar names may also be used for cells that can be employed in addition to a macro cell, such as micro cell, femto cell, etc.
It is generally believed that the majority of radio traffic will be generated in indoor environments, and in this respect certain buildings or otherwise well-defined locations can be identified as hot spots in terms of expected traffic intensity. In that case, the above-described small cells may be created to off-load larger macro cells of a cellular network by providing multiple low-powered access points in a building inhabited or visited by several terminal users. The term “local site” will be used in this disclosure to represent any such limited and well-defined location, either indoor or outdoor, public or private, in which access points are installed to cover small cells located within or close to a macro cell area. Further, the term “mobile terminal” will represent any device or user equipment capable of radio communication with the above access points, including but not limited to mobile phones, smartphones, laptops and tablets.
At such a local site, one or more access points with antennas can be installed which are connected to a core part of the cellular network, e.g. via switches or the like. The local site discussed in this disclosure may be an office of an enterprise or an organization, a hotel, an airport, a shopping mall, a residence, a building with several apartments, to mention a few non-limiting examples. When communicating over an access point installed in a local site, the mobile terminals are often situated quite close to the access point antenna and relatively low transmission power is therefore usually sufficient to achieve proper signal reception, either at the mobile terminal for downlink signals or at the access point for uplink signals, thus typically not causing much radio interference in the cellular network. Further, radio communication over access points covering a limited area of a local site is appropriate also because mobile terminals are typically not fast moving when present in such locations.
FIG. 1 illustrates a conventional arrangement of a local site 100, here illustrated as a building, having multiple access points 102 connected to a base station 104 or the like which provides a link to a core part 106 of a cellular network which in turn is connected to various service providers and other services networks, e.g. over the Internet, which in this context are schematically represented as a “service edge” 108. The service edge 108 may be comprised of various servers, switches, routers and other network or service provider components which are not necessary to outline in any detail in this disclosure.
In this example, three exemplifying access points 102 are shown, each comprising at least an antenna and a radio unit, which are connected to the base station 104 being installed at the local site, e.g. in the basement of the building. Three mobile terminals T1, T2 and T3 are also shown being connected to respective access points 102. In this scenario, any signals to or from each mobile terminal are routed over the base station 104 and the core part 106 of the cellular network. Any number of further local sites 110 may be served by the core part 106 in a similar manner.
It is quite common, at least in certain types of local sites, that two mobile terminals in the same local site communicate with each other. In the example shown in FIG. 1, terminals T1 and T3 communicate with each other and the signals back and forth in this communication are conventionally routed via the base station 104 over the core part 106 and back again to the local site 100, as illustrated by the dotted line 112, thus forming a “trombone-like” signal path over the core part 106.
FIG. 2 illustrates another proposed arrangement in a local site 100, using the same numerals for similar components as in FIG. 1, where the above-described “tromboned” signal path is avoided by routing the signals locally by the base station 104 over a local or proprietary network 200 with one or more servers and switches that can be used to serve the terminals locally within the local site, if applicable. The base station 104 is able to determine that one or more mobile terminals can be served locally by equipment present within the local site 100, e.g. when two terminals T1 and T2 communicate with one another as in the previous example. In this example, the signals communicated between terminals T1 and T2 are routed over the base station 104 but not over the core part 106 of the cellular network, as illustrated by the dotted line 202, and very limited resources in the core part 106, e.g. in a Home Subscription Service, HSS, need to be occupied for setting up the signal flow. Another example where this can be employed is when a locally served mobile terminal is in communication with a server connected to the local network 200, which server could be placed in the local site 100 or be connected thereto. The traffic between the terminal and such a server could be routed over the local network 200 via the base station 104, without going over the cellular network's core, in the manner described above.
Since the radio traffic over the access points 102 takes place over a frequency spectrum allocated to, and paid by, the cellular network, it is natural that the operator of the cellular network wants to control the usage of radio resources within that frequency spectrum at the local site in order to coordinate it with the usage of radio resources in other parts of the network and to optimize the capacity and quality in the network. For example, the operator typically wants to control and schedule radio resources to different mobile terminals at the local site 100 in a way that minimizes the amount of harmful interference between different radio communications and to use the limited amount of radio resources efficiently in the network. The base station 104 is therefore typically controlled by the operator of the cellular network, unless base station 104 is isolated from the macro node covering the area.
However, it is a drawback that the above-described conventional arrangements of FIGS. 1 and 2 and others require a fully equipped base station at the local site, which is quite costly to install and maintain. In order to reduce the costs for deploying access points at local sites for radio communication, it has been suggested to move at least some costly parts of the base station to a more centralized location such as a central office or the like which can serve several such local sites.
An example of this is shown in WO 2004/019624 A1 where costly installations at a local site are avoided by placing the radio equipment of a base station in another location remote from the local site where the antennas are located. In this way, the costs for deploying extensive radio coverage in indoor locations and other local sites where heavy traffic is expected, can be reduced, particularly if a local infrastructure with antennas and cables is already in place such as when a local broadband access has been installed. However, when the base station is located remote in this way, it is not possible to avoid tromboning with the above-described solution of FIG. 2 since that would still require a fully equipped base station at the local site.